Wear Behavior Of WC Research Articles

Wear Behavior of WC–Cu Deposited ZE41A Magnesium Alloy Using Wear Mechanism Map

The present investigation studied the dry sliding wear behavior of WC–Cu deposited ZE41A magnesium alloy under various parameters such as normal load, sliding speed and sliding time and the responses are wear rate and coefficient of friction. In this investigation, WC–Cu deposited magnesium alloy specimens were tested using pin on disc apparatus against EN31 steel disc. Wear mechanism map is developed for wear rate of the deposited magnesium alloy against normal load and sliding speed to identify the different wear modes such as mild, severe and ultra sever wear. Worn surface samples is assessed by Scanning Electron Microscope (SEM) and Energy Dispersive Spectroscope (EDS) to confirm the different wear mechanism such as abrasion, oxidation, delamination and melting. Normal load is identified as the most dominant process parameter in this experiment. Magnesium alloy deposited using WC–Cu composite coating by EDC improved the wear behavior in the lower ranges of sliding conditions.

UNSM 기술을 이용한 초경의 기계적 특성변화

In this study, an ultrasonic nanocrystalline surface modification (UNSM) technique is applied to tungsten carbide-cobalt (WC-Co) to extend the service life of carbide parts used in press mold. The UNSM technique modifies the structure, reduces the surface roughness, increases the surface hardness, induces the compressive residual stress, and increases the wear resistance of materials by introducing severe plastic deformation. The surface roughness, hardness, and compressive residual stress of WC after UNSM treatment improve by about 42, 10, and 71%, respectively. A wear test under dry conditions is used to assess the effectiveness of the UNSM technique on the friction and wear behavior of WC. The UNSM technique is found to reduce the WC friction coefficient by approximately 21% and enhance the wear resistance by approximately 85%. The improved friction and wear behavior of WC may be mainly attributed to the increased hardness and compressive residual stress. Moreover, the WC specimen is treated by UNSM technique using three different WC, silicon nitride (Si3N4) and stainless steel (STS304) balls. The surface treated by WC balls shows the highest hardness when compared with treatment by stainless steel and silicon nitride balls. According to the obtained results, the UNSM technique is believed to increase the durability of the carbide component by improving the friction and wear behavior.

Wear behaviour of WC–Co HVOF coatings at different temperatures in air and argon

The wear behaviour of tungsten carbide–cobalt (WC–Co) high-velocity oxy-fuel coatings within the range of room temperature (RT) to 800°C in air and RT to 650°C in argon was studied using a ball-on-disc tribometer. The worn track morphologies, compositions and oxide phases after the tests were analysed by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction analysis and Raman spectroscopy. The correlation between the oxidation and wear of WC–Co coatings was investigated. Results show that oxides, as well as the oxidation of coatings, have an important role during the tribological process of WC–Co coatings. The volume loss of WC–Co coatings in air is low at RT to 600°C, which indicates that oxidation inhibits wear. Friction promotes the formation of CoWO4. CoWO4 can reduce friction and wear, and enables the coating to maintain good tribological properties even at 600°C. Above 600°C, the coating oxidises vigorously and its property deteriorates rapidly, which cause serious wear. In argon, the volume loss of WC–Co coating is significantly higher than that in air at RT to 600°C. Wear decreases as temperature rises because of the gradual formation of oxides. Consequently, WC–Co coatings should not be used as wear-resistant coatings in O-deficient environments at RT or at elevated temperatures.

Effect of heat treatment on wear behaviour of WC–(W,Cr)2C–Ni coating

Tungsten carbide (WC)–(W,Cr)2C–Ni coatings have been deposited by high velocity oxyfuel spraying. The influence of post-vacuum heat treatment on the microstructure, phase composition, microhardness and wear resistance of the coatings has been investigated, which is conducted based on analyses of the microstructure and phase composition evolution of the coatings by scanning electron microscopy and X-ray diffraction, as well as measurement of their microhardness with a microhardness tester and evaluation of their friction and wear behaviour with an oscillating friction and wear tester. Results show that after heat treatment above 600°C, crystallisation of amorphous phases occurs, and some new phases rich of Fe and C are generated in the coatings. Moreover, the microhardness and wear resistance of WC–(W,Cr)2C–Ni coatings increase with increasing heat treatment temperature up to 600 and 700°C, but they tend to decrease with further elevating heat treatment temperature.

Friction and wear behaviour of WC–Co–Cr3C2–VC cemented carbides obtained from nanocrystalline mixtures

Abstract The effect of adding Cr 3 C 2, VC or a mixture of both as a grain growth inhibitors to cemented carbides obtained from WC–12 wt.%Co nanocrystalline mixtures on the behaviour of friction and dry sliding wear have been studied. All the wear tests were performed on a tribometer with ball on disc configuration, using a WC–6 wt.%Co ball as a counterpart with normal contact loads of 40 and 60 N, sliding distance of 2000 m and a sliding speed of 0.1 m/s. A significant reduction in the wear rates was observed by the effect of the aforementioned additives, in particular for the VC, which showed an increase in the wear resistance of the order of 90%. The analysis of wear and surface damage were correlated to the observed behaviour.

Microstructure and high-temperature friction and wear behavior of WC-(W,Cr)2C-Ni coating prepared by high velocity oxy-fuel spraying

WC-(W,Cr)2C-Ni coating was prepared by high velocity oxy-fuel spraying (HVOF). The microstructure and phase composition of the as-sprayed coating and that after oxidation at high temperature were analyzed by means of scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The oxidation behavior of as-sprayed coating and starting powders was evaluated by thermogravimetry. Dry sliding friction and wear behavior of the WC-(W,Cr)2C-Ni coating sliding against Si3N4 ball at different temperatures (room temperature 20°C and elevated temperature of 700°C and 800°C) was evaluated using an oscillating friction and wear tester. Besides, the microhardness and fracture toughness of the coating was also measured. Results show that sintering agglomerated WC-20wt.%Cr-7wt.%Ni powder is an effective method to prepare agglomerated and sintered WC-(W,Cr)2C-Ni composite powder. The excellent oxidation resistance of WC-(W,Cr)2C-Ni coating is mainly resulted from a double-decker shell-core microstructure formed in the coating. The composition of the outer shell is (W,Cr)2C phase and that of the inner shell is Cr3C2. During high-temperature friction and wear test, well remained hard WC phase in the WC-(W,Cr)2C-Ni coating can guarantee its good mechanical properties and wear resistance, and newly generated nano NiWO4, CrWO4 and Cr2WO6 particles can further improve these properties significantly.

Effect of carbide grain size on microstructure and sliding wear behavior of HVOF-sprayed WC–12% Co coatings

In order to examine the effect of carbide grain size on the wear behavior of WC–Co coatings, coatings with low degree of decomposition of WC were thermally sprayed by a high-velocity oxy-fuel (HVOF) system from three agglomerated WC–12% Co powders with various carbide size distributions. Characterization of the coating showed that the average carbide grain sizes of the coatings were 0.8, 1.4 and 2.8 μm and that a decrease in carbide grain size led to slightly higher degree of decomposition of WC. Dry sliding friction and wear tests using sintered alumina (Al 2O 3) as the mating material were performed. The coefficient of friction of the coatings was nearly constant regardless of the test conditions and carbide grain sizes. The specific wear rate of the coatings was very low ∼10 −6 mm 3/(Nm) and increased with increasing carbide grain size. The microscopic analyses of the worn tracks have shown that binder extrusion followed by carbide removal or carbide fracture are the dominant material removal mechanisms. The extruded cobalt acts as binder to form a ductile, dense and well cohered tribofilm on the worn surface to protect the surface from further wear, decreasing the wear rate of the coatings. Because a pull-out of single carbide particle provides less damage to the finer coating and also because the debris consisting of finer carbides are less effective as the third-body abrasions, the wear rate decreases with decreasing carbide size in the coatings.